The invention concerns a mixed propulsion system for a seagoing vessel.
In particular the invention relates to a power management arrangement for a ship propulsion system having a mix of prime movers that is several prime movers powered from several different fuel sources. Ship operators require flexible and efficient propulsion plant that is able to accommodate a range of ship operating profiles and speeds, and to be capable of delivering sufficient power on demand in all situations. A number of power sources operating on different fuels are available, each having its individual advantages and weaknesses.
A marine power system is required to meet a number of challenges: it must be capable of meeting ship power requirements at all times and in all conditions, but ship owners and operators also demand economic operation, to be able to meet environmental legislation and economy of cargo space. The instantaneous power demand varies throughout the different stages of a voyage. In port and loading cargo where propulsion is not required the system has to meet a demand comprising the ship's domestic requirement and that of its cargo handling equipment. Maneuvering at low speed when leaving and entering moorings, harbours etc. the propulsion system requires a potentially wide range of power demand levels which may change in an instant. Whereas at sea the power demand may remain more or less constant for many hours or even several days at cruise speeds.